The 945P chipset has a list of supported CPUs. Here it is -> http://www.intel.com/Products/Desktop/Chipsets/945P/945P-overview.htm
http://compare.intel.com/pcc/showchart.aspx?mmID=8764&familyID=10&culture=en-US
So it's possible it does but only Dell could rule on this. Or just try it.
Bob
Has anyone been able to upgrade thier old xps400 from the 2.8ghz pentium d to the an intel e2200 core 2 duo? I think my mobo fsb speed is maxed out by the bios at 800 so this processor should in theory be able to run. Same socket design is used as in the pentium d. Would be a nice improvement in performance for just 40-50 dollars!

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic